What is lactic acid known to cause in muscles?

Lactic acid is a byproduct of anaerobic metabolism, which occurs when muscles use glucose for energy in the absence of sufficient oxygen. This process is particularly active during intense exercise. The accumulation of lactic acid in muscle tissue can lead to a sensation of soreness. This occurs because lactic acid can irritate the muscle fibers and contribute to the body's response to exercise-induced stress.

It is important to note that while lactic acid is associated with fatigue and is often mentioned in discussions about muscle cramps and weakness, it is primarily the soreness experienced after intense workouts that is most directly linked to its buildup. Once the body clears lactic acid from the muscles, the soreness typically diminishes, which is why it is often perceived as a temporary condition associated with high levels of exertion.